Essence of man: Y size doesn't matter

The Y chromosome, which makes men male, has been shrinking for 180 million years. But there's more to this rotting husk than anyone suspected

THERE'S nothing very macho about the Y chromosome. Even though it's what makes men male, the human Y, like its counterparts in almost all mammals, is tiny compared with its partner, the X chromosome. It's lost hundreds of genes – and if the Y continues to lose them, it could someday wink out of existence entirely.

Claims of its impending demise are starting to look premature, however. Far from being a rotting husk, the modern Y, tiny though it is, is turning out to be a highly evolved and surprisingly important part of men's wider genetic endowment, responsible for far more than just maleness.

It is easy to see why some biologists thought the Y was destined for ...

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